Recovery of a polymer contained in the polymer solution produced by solution polymerization is ordinarily achieved by washing the polymer solution with water to decompose a catalyst residue and the like and remove, and devolatalizing a volatile component such as solvent, unreacted monomers and remained water in a small amount to remove from the polymer solution. In addition, this devolatalization is conventionally performed by a method in which the polymer solution is concentrated in advance according to a flash evaporation method or the like and then the solvent is removed by steam stripping, and the like. This steam stripping is performed by supplying steam to a desolvation tank ordinarily from a bottom portion thereof and then allowing the solvent and steam to contact, however, in the case only one desolvation tank is used, there is a case in which the system in the desolvation tank is in an equilibrium state and the desolvation can not efficiently be performed. Thus, a method for performing a multiple-step desolvation by using a plurality of desolvation tanks connected in series with one another, ordinarily, two desolvation tanks has been proposed and is in a practical use (for example, referred to non-patent document 1).
[Non-Patent Document 1]
“Petrochemical Process” compiled by the Japan Petroleum Institute, Continuous polymerization process flow of BR, FIG. 13.1, p. 334, Kodansha Publishing Co., Aug. 10, 2001.